1. Field of the Invention
The present invention relates to a switch device to be mainly used to operate the air-conditioner or audio equipment for a vehicle.
2. Background Art
In recent years, an increasing number of vehicles have switch devices including a various kinds of operating bodies on the front panel in the vehicle cabin for the operation of various kinds of electronic devices, such as an air-conditioner and audio equipment.
A description is provided of such a conventional switch device with reference to FIGS. 6 and 7.
FIG. 6 is a sectional view of a conventional switch device. FIG. 7 is an exploded perspective view of the conventional switch device. With reference to FIGS. 6 and 7, downwardly-projecting hollow cylindrical part 1A is formed on the bottom face of columnar operating body 1 made of an insulating resin. On the outer periphery of hollow cylindrical part 1A, a plurality of notches 1B are provided.
Operating shaft 2A of switch 2 is columnar and projects upwardly. Formed in switch 2A are a plurality of switch contacts (not shown) to be brought into or out of electrical contact with each other by rotation of operating shaft 2A. Operating shaft 2A having flat part 2B on the side face thereof is inserted in hollow cylindrical part 1A on the bottom face of operating body 1.
Spring member 3 is made of a helically wound metal wire. Spring member 3 is placed on the outer periphery of hollow cylindrical part 1A in substantially a yielding state. Hollow cylindrical part 1A is fastened by operating shaft 2A to form the switch device.
When such a switch device is assembled, first, spring member 3 is placed on the outer periphery of hollow cylindrical part 1A on the bottom face of operating body 1. Thereafter, while hollow cylindrical part 1A and spring member 3 are expanded outwardly, operating shaft 2A of switch 2 is press-fitted into hollow cylindrical part 1A.
Such a switch device is mounted on circuit board 4 having a plurality of wiring patterns (not shown) on both sides thereof, by soldering or other methods. The switch device is placed in the front panel or other parts in a vehicle cabin. At this time, switch 2 is electrically coupled to various kinds of electronic devices, such as an air-conditioner and audio equipment, or electronic circuits (not shown) of the vehicle, via connectors or leads (not shown).
In the above structure, rotary manipulation of operating body 1 rotates operating shaft 2A press-fitted into hollow cylindrical part 1A on the bottom face of operating body 1, thereby bringing switch contacts in switch 2 into or out of electrical contact with each other. The signals generated at this time are fed into the electronic devices or electronic circuits, thus changing the temperature of the air-conditioner, or the volume of the audio equipment.
In this case, flat part 2B formed on the side face of operating shaft 2A prevents operating body 1 and operating shaft 2A from turning separately with normal operating force. However, in the upward pulling direction, hollow cylindrical part 1A is fastened onto operating shaft 2A by the yielding force of spring member 3 only. Therefore, pulling operating body 1 with strong force may remove operating body 1 from operating shaft 2A.
Increasing the fastening force of spring member 3 to prevent this phenomenon enhances resistance to pull-out of operating body 1. However, when operating body 1 and switch 2 are assembled, press-fitting operating shaft 2A into hollow cylindrical part 1A by hands is difficult and jigs are necessary for the assembly.
As described above, in the conventional switch device, increasing the fastening force of spring member 3 to prevent the pull-out of operating body 1 makes the assembly of operating body 1 and switch 2 difficult and necessitates more assembly time.
The technique of the conventional switch device is disclosed in Japanese Utility Model Unexamined Publication No. H02-23718, for example.